We on the Google Calendar team work hard to play well with others, so you can synchronize your calendars with a number of mobile devices and desktop applications. This way, you can choose whichever calendars you want to use and keep all of them up to date. Most of these options have been around for a while, and we're happy to announce that Google Calendar now supports the CalDAV protocol -- an evolving, open standard for calendar synchronization.

Apple iCal and Mozilla SunbirdYou can now sync your calendar with applications that support CalDAV, such as Apple's iCal and Mozilla's Sunbird. Learn more about how to get started in our help center.

Microsoft OutlookGoogle Calendar Sync for Outlook lets you sync events between Google Calendar and Microsoft Outlook Calendar. You determine the direction of information flow, as well as the sync frequency. It's compatible with Microsoft Outlook versions 2003 and 2007, and operating systems Windows XP and Windows Vista.

BlackBerry mobile devicesIf you carry a BlackBerry smartphone, Google Sync for BlackBerry synchronizes your device's native calendar with Google. You can access your Google Calendar even when you don't have network coverage and get alerts for upcoming appointments with sound or vibration. It automatically runs in the background, so you can attend to other tasks and still be reminded of your appointments.

Android devicesIt's easy to connect an Android-powered phone to Google Calendar using the phone's preloaded Calendar application. New events are pushed in real-time to your phone and any changes you make on-the-go are immediately available on the web.

If you have another mobile device, just visit calendar.google.com from your phone, and you'll get a special version of Google Calendar optimized for the small screen.

Gmail fans have been building unofficial extensions to spice up their inboxes for a while, but up til now themes haven't been an integral part of Gmail. We wanted to go beyond simple color customization, so out of the 30 odd themes we're launching today, there's a shiny theme with chrome styling, another one that turns your inbox into a retro notepad, nature themes that change scenery over time, weather driven themes that can rain on your mailbox, and fun characters to keep you in good company. There's even an old school ascii theme (Terminal) which was the result of a bet between two engineers -- it's not exactly practical, but it's great for testing out your geek cred. We've also done a minor facelift to Gmail's default look to make it crisper and cleaner -- you might notice a few colors and pixels shifted around here and there.

As you can see from these photos taken around our office in Zurich, Switzerland, themes have made their way into more than our inboxes -- that's a character from the ninja theme made out of pixel blocks, customized laptop decals, and a giant Zoozimps character on a beam next to my desk:

To customize your inbox, go to the Themes tab under Settings. We'll be rolling out themes to everyone over the next couple of days, so if you don't see them yet, check back soon. As for which theme to choose, don't ask us. We're neutral ;)

I'm a big user of Gmail chat. Being able to switch from email to chat as needed, all within the same app, is really great for productivity. But people can only type so fast, and even with our new emoticons, there are still some things that just can't be expressed in a chat message.

That's why today we're launching voice and video chat -- right inside Gmail. We've tried to make this an easy-to-use, seamless experience, with high-quality audio and video -- all for free. All you have to do is download and install the voice and video plugin and we take care of the rest. And in the spirit of open communications, we designed this feature using Internet standards such as XMPP, RTP, and H.264, which means that third-party applications and networks can choose to interoperate with Gmail voice and video chat.

Once you install the plugin, to start a video chat, just click on the "Video & more" menu at the bottom of your Gmail chat window, and choose "Start video chat." You'll have a few seconds to make sure you look presentable while it's ringing, and then you'll see and hear your friend live, right from within Gmail. You can click the "pop-out" iconto make the video larger, or click the fullscreen iconin the upper left-hand corner for a fully immersive experience. See this all in action in the video below:

Our team is spread between Google offices in the US and Sweden, and video has really changed the way we work. Collaborating across continents and timezones is a fact of life for us, and it sure is easier (and greener) to click "Start video chat" than to get on a plane! And when I do have to visit another Google office, I can use Gmail voice and video chat to check in with my family.

We've just started to roll out Gmail voice and video chat for both PCs and Macs, so if you don't see it right away, don't worry -- it could take a day or so for this feature to be available in all Gmail and Google Apps accounts. If you want to download the plugin right away, visit http://gmail.com/videochat. And if you need a webcam, there are a few models with special discounts through November 30th (I use the QuickCam Pro 9000 myself).

Are you addicted to email? Do you keep Gmail open on your browser, constantly hitting refresh to get your latest messages?

If you're using Google Toolbar 5 for Internet Explorer (or Toolbar's Firefox version), you can add the Gmail custom button to make your life easier. With the Gmail button, you can get new message alerts, see previews of your mail and use Toolbar's search box to find any message no matter what page you're on.

Google Toolbar also has a "Send to" feature: when you click on the "Send to" icon, a Gmail compose window opens that automatically includes a link to the page you're currently on and any text you have highlighted on that page. This makes it easy to email your friends interesting pages you come across as you browse the web.

Plus, you can also add Google gadgets to your Toolbar to bring your favorite websites and online services closer to you. One of my favorites is the Google Calendar gadget: by clicking on the calendar icon, I can check out my schedule for the next few days and even add events.